Although several studies have reported relaxing and stimulating effects of odors on physiology and behavior, little is known about their underlying mechanisms. It has been proposed that participant expectancy could explain these activation effects. Since emotional stimuli are known to modulate time perception, here we used the temporal bisection task to determine whether odors have objective relaxing and stimulating effects by respectively slowing down or speeding up the internal clock and whether prior expectancy could alter these effects. In Experiment 1, 118 participants were presented either with a strawberry odor or an odorless blank. In Experiment 2, 132 participants were presented either with a lemon odor or an odorless blank. In both experiments, expectancy was manipulated using suggestion (verbal instructions). The stimulus was either described as relaxing or stimulating, or was not described. In the absence of prior suggestion, findings showed that, compared to participants presented with an odorless blank, participants presented with the strawberry odor underestimated sound durations (i.e., a relaxing effect) whereas participants presented with the lemon odor overestimated them (i.e., a stimulating effect). These results confirm that pleasant odors can have objective relaxing and stimulating effects by themselves, which are better explained by arousal-based mechanisms rather than attentional distraction. Furthermore, in both experiments, incongruent suggestions undid the effects of both odors without reversing them completely (i.e., strawberry did not become stimulating even if participants were told so). Both these bottom-up and top-down influences should be considered when investigating the emotional impact of odors on human behavior.

尽管有几项研究报告了气味对生理和行为的放松和刺激作用，但对其潜在机理知之甚少。已经提出，参与者的期望可以解释这些激活效应。由于已知情绪刺激会调节时间知觉，因此在这里我们使用时间二等分任务来确定气味是否分别通过减慢或加快内部时钟的速度来达到客观的放松和刺激效果，以及先前的期望是否会改变这些效果。在实验1中，向118位参与者展示了草莓味或无味的空白。在实验2中，向132位参与者展示了柠檬味或无味的空白。在两个实验中，使用提示（口头指示）来操纵期望值。刺激被描述为放松或刺激，或未描述。在没有事先建议的情况下，研究结果表明，与呈现无味空白的参与者相比，呈现草莓气味的参与者低估了声音的持续时间（即放松效果），而呈现柠檬气味的参与者高估了声音的持续时间（即刺激性）。影响）。这些结果证实，令人愉悦的气味本身可以具有客观的放松和刺激效果，这可以通过基于唤醒的机制而不是注意力分散来更好地解释。此外，在两个实验中，不一致的建议消除了两种气味的作用，而没有完全消除它们（即，即使告知参与者草莓也没有刺激性）。